Data Dependence Relation Analysis and Concurrent Extraction of Ladder Diagram

Program dependence relation analysis is an important method of testing, maintaining, analyzing and optimizing program, especially parallel extraction. The dependence of rungs caused by definition and reference has the same variable and the parallelism of sequential rungs in Ladder Diagram(LD). Aiming at the problem, a method is proposed to extract LD diagram rung data flow and data dependence relation by constructing data dependence relation directed diagram, recognize LD diagram parallel rung in data dependence relation directed diagram. Experimental result shows that the LD diagram scan time is shorten to 50%~20% by concurrent extraction.